This invention relates to thin absorbent panty liners for protecting the wearer's undergarment both during intermenstrual use and, in conjunction with other catamenial devices, during menstrual use.
Several products are now on the market to provide the user with protection from the staining of undergarments, and particularly during non-menstruating days. These products generally are designed to be worn in the crotch portion of an undergarment and comprise a body facing side which is pervious to body fluids, an absorbent body which is capable of absorbing and retaining quantities of body fluid and a fluid impermeable backing on the garment facing side of the product for presenting the fluid absorbed and retained from "striking through" onto the crotch surface of the undergarment. Generally these products have been provided with a layer of pressure-sensitive adhesive for adhering the product to the crotch portion of the garment.
In the main, these intermenstrual products utilize materials of construction similar to the larger menstrual products in popular use. Accordingly, the fluid impermeable backing designed to prevent strike through comprise a totally fluid occlusive polymeric film with a film of polyethylene being the material of choice. Several drawbacks have been discovered when using such totally fluid occlusive products. In contrast to the forerunner menstrual products, the intermenstrual products of concern herein are designed to be worn every day and to be changed much less frequently than the menstrual products. Accordingly, body fluids absorbed by the products will remain carried by the wearer throughout the day and eventually, should such intermenstrual discharges be voluminous or should the wearer perspire heavily, the products will actually accumulate wetness which will add to, rather than obviate, user discomfort. The accumulation of body fluid for an entire day may even cause the product to become saturated toward the end of the day and fail, allowing body fluids to stain the undergarment and possibly embarrass the wearer. Still further, the accumulation of body fluids, particularly in aqueous solution, lends itself to the breakdown of these fluids and the proteanacous matter associated therewith into odiferous compounds which can cause embarrassment. While the odors can be masked by the use of perfumes and the like, such masking is dependent on the volatilization of the essential oils in the perfume and the fluid occlusive films used heretofore as backings for these products tend to frustrate such volatilization and inhibit the masking effect of such perfumes.
Several prior suggestions exist in the art of catamenial napkins and diapers for rendering a relatively liquid impervious polyethylene film, pervious to water vapor transmission. For example, in U.S. Pat. No. 3,989,867 issued to J. B. Sisson on Nov. 2, 1976 a polyethylene backing sheet is described having cone shaped bosses which will allow water vapor to evaporate from the surface of the absorbent material in a diaper, catamenial napkin or dressing. The actual open surface of such a backing is said to be from about 1/2% to about 10%. As such, it is clear that at least 90% of the backing is in fact impervious. As is recited in the above set out patent such a system is said to allow the evaporation of substantial quantities of liquid from such products as diapers where the products have relatively thick absorbing pads and the quantity of liquid deposited therein is substantial. Undoubtedly, this is because sufficient liquid is deposited to essentially wet through local areas of the absorbent and create, by wicking, a wet area at the interface between the backing and the absorbent body which is large enough to span several of the cone shaped bosses. Unfortunately, this situation does not exist for the panty liners which are the subject matter of this invention. In this latter case, the deposition is slight and the area of the pad, in contact with the backing, that is wet with liquid, is small. Thus, in the panty liners of this invention, very little wet interfacial surface would be in contact with open backing surface having what may be considered macropores and hence little evaporation occurs.
To obviate this problem, a requirement for the backing would be to increase the open area of the polymeric film and, of course, this must be done without creating large pores which will result in strike through. One such backing exists in the surgical dressing art and is described in U.S. Pat. No. 3,426,754 issued on Feb. 11, 1969 to Harvey S. Bierenbaum, et al. Described therein is a polymeric film having what is termed micropores i.e., extremely small openings. Unfortunately such a material is prohibitively expensive when employed in products such as the panty liners considered herein which are designed to be used daily and then disposed of.
Accordingly, there is a need for a product especially designed for daily intermenstrual wear.